The present invention relates to a method for the decontamination and detoxification of substances, in particular of seeds such as rice, buckwheat, legumes, nuts or the like, and of cereals, in particular maize, wheat, oats, barley, rye which are contaminated with mycotoxins, such as for example aflatoxins, zearalenones or ochratoxins, in particular with tetracyclic trichothecene mycotoxins of the general basic formula ##STR1## with the radicals R.sub.1 to R.sub.5 being described by the various trichothecene mycotoxins, such as for example T-2 toxin (T-2), HT-2 toxin (HT-2), diacetoxyscirpenol (DAS), monoacetoxyscirpenol, neosolaniol, nivalenol (NIV), deoxynivalenol (DON), 3-acetyldeoxynivalenol (3-AcDON), T-2 tetraol, scirpentriol, fusarenon, crotocin, satratoxin H etc.
Aflatoxins, zearalenones and ochratoxins have quite different chemical structures when compared with the trichothecenes, but have in common with them an ester or lacton structure element in the molecule which is reactive and which can for example react with compounds with a primary or secondary amino function to form the corresponding amides.
Trichothecenes are sesquiterpenoid compounds with a C12, C13 spiroepoxy group which are produced by fungi such as fusarium, trichothecium, myrothecium, stachybotrys and other. Rice and different cereal types, in particular maize, wheat, oats, barley and rye, are contaminated depending on the kind of species, climatic conditions and nature of the ground by these fungi and are in this way contaminated with secondary metabolic products, with the mycotoxins, such as the trichothecene type. These mycotoxins cause various trichothecene toxicoses, both in animals when the contaminated cereal is used as feed and also in humans.
The various trichothecenes act in different concentrations in such a way that they cause cell damage, are neurotoxic and dermatoxic and lead to a rejection of the feed, to sickness and diarrhea. Over a longer period of time relatively large quantities of mycotoxins can be passed on, especially to animals, via the feed or feed cereals and even by those having a small mycotoxin contamination and this often leads to serious disorders (see "Mycotoxins in Food", P. Krogh, Edt., Academic Press, New York, 1987). The fungi which deliver the trichothecenes generally already contaminate the cereal in the field and can however also remain active with incorrect storage of the cereal (for example cool and moist). One can perhaps control the storage conditions but not however the contamination in the field so that this also depends strongly on climatic conditions.
A harvest which is strongly contaminated with mycotoxins is hardly usable and leads to substantial economic damage. In particular this also applies to maize and wheat which are used in large quantities in the feed industry. As investigations show (Hart and Braselton, J. Agric. Food Chem. 31, 657 (1983)) the dry milling process of wheat which was for example contaminated with DON admittedly leads to a partial separation of DON richer and DON weaker flour and meal, however in any event DON remains in the end product. The same also applies to maize products.
Trichothecenes are chemically relatively stable, in particular the toxophor group, the 12,13 epoxide. Thus the deoxynivalenol (DON) is hardly broken down even with cooking, roasting and baking conditions and also during autoclaving or steam treatment (toasting, pelleting, extruding) and thus also remains in existence in a prepared feed or foodstuff. That is to say, no detoxification is achieved in this way (see A.El-Banna et al., J. of Food Protection 46 (6) (1983)). Trichothecenes which contain an ester group are converted in the alkaline mixture into the corresponding alcohols, however the toxicity of the decomposition products obtained in this way is mainly high and is generally hardly reduced via this decomposition route (see "Mycotoxins in Food" and citations therein).
Since it is only in the last few years that it has been fully recognized that especially DON and also 3-AcDON occur in previously unknown high concentrations on maize and other cereals, increased importance is placed on investigation of the products with regard to the DON content and the legislatory authorities in the various countries are beginning to react to this. There are however as yet no binding regulations on upper limits for the content of trichothecene mycotoxins. However, on the basis of toxicological data (see "Mycotoxins in Food", chapter 6 "Thrichothecenes in Food") it is recommended that for example the values of 2 ppm (1 ppm) for DON and 0.2 ppm for nivalenol should not be exceeded. Since small children and children react considerably more sensitively to mycotoxins, the limit for children's food should be set substantially lower. The same applies for animal feeds which are used with young animals, and in this case attention should also be paid to the consumption of animal feed over a long period of time. The extent to which the trichothecenes experience an increase in activity through other micotoxins, or vice versa, is still largely unclear, however one is aware of a possibly enhanced health risk.
For the above named reasons, increased importance is attached to the development of methods for reducing the mycotoxin content of the cereals and, as a consequence, of cereal products.
As a result of the high toxicity of mycotoxins of the aflatoxin type, which represent metabolic products of storage fungi (for example aspergillus types), the development of methods for the decontamination of products containing aflatoxins, such as for example peanut meal, maize and other cereals, stands in the foreground. Based on the chemical structure of aflatoxins (contained in one lacton ring) processes which concern the treatment of the material with an amine (for example ammonia or monomethyl amine) in a strongly alkaline medium (for example with Ca(OH)2 or NaOH) at an elevated temperature (for example 100.degree. C.) and under pressure (for example 3 to 10 bar) for half an hour to several hours have shown themselves to give the desired end result (see I. Apelt, Die Muhle+Mischfuttertechnik, year 126, No. 30, 435 (1989)). This strongly alkaline treatment of the cereal or of the nut meal with an amine additive (ammonia or methylamine) and with a possible further assistance of formaldehyde (method currently in use in France) is hitherto the only relatively certain and practicable way of detoxification of aflatoxins, zearalenones and ochratoxins.
As treatisees describe, the detoxification of fusarium toxins such as T-2 toxin, diacetoxyscripenol and zearalenone can also be achieved under these conditions (see J. Bauer et al., Tierarztl. Umschau 42, 70-77 (1987)). In the context of a symposium "undesired substances in foodstuffs, mycotoxins in cereals and animal feeds--methods for their removal" held in Braunschweig 30./31.10.1990 (see IFF/Informationsdienst No. 224/1990) it was reported that in addition to the fusarium toxin deoxynivalenol (DON) also zearalenone, ochratoxin and aflatoxin could be largely removed by the alkali/amine treatment of cereals under pressure and at 95.degree. C.
From the existing prior art it can be seen that a detoxification of the mycotoxins such as aflatoxin B1, T-2 toxin, diacetoxyscirpenol, deoxynivalenol and zearalenone (a likewise relatively frequently encountered mycotoxin on cereals) and also ochratoxin (a mycotoxin produced by storage fungi) can, as examinations of the materials show, largely be achieved after the physical-chemical and also biological processes. The treatment conditions (strongly alkaline, addition of amines, optionally addition of formaldehyde, high temperature T&gt;90.degree. C. and pressure) are however to be regarded as drastic from a chemical viewpoint. The quality evaluation of cereal and feed samples treated in this way was not described, however from our own experience, a partial change of the color, taste and quality of the products certainly takes place.
In DE 40 19 996 A1 there is described a method of cleaning fruits and vegetables from contaminants such as mud, biological contamination, microbiological flora, such as mold fungi, fungi, worms, bacteria, microbes and also chemicals such as pesticides, fertilizer residues and the like from the rough or smooth surfaces of fruits and vegetables of all kinds. In this method the fruits to be cleaned are introduced into a tank filled with water and are subjected to an ultrasonic oscillation field. During this a mixture of cleaning, floatation and disinfection agents can be added to the water.
This known method serves to free fruits and vegetables which are to be processed in the kitchen from the customary contamination and is intended to replace the washing off which is normally done by hand or by means of hydromechanical cleaning devices.
The decontamination and detoxification of cereals or other seeds intended as foodstuffs are however not addressed. In particular a reference can be found in the method described in DE 40 19 996 A1 as to how toxic metabolic products of mold fungi, in particular of mycotoxins, can be decontaminated and/or removed from fruits and vegetables. Moreover, the treatment of cereals and other seeds serving as foodstuffs is not explained.
In DE 19 14 095 A1 there is further described a method for decontamination of oil-containing or fat-containing foods, such as for example nut kernels or cereals or cereal products containing aflatoxins. In this process the material containing the poison is washed or sprayed with warm water or water vapor and is subsequently rinsed with water at room temperature or below. The washing and rinsing takes place on a vibrating channel on a vibrating sieve, with the material to be treated being subjected during the washing process to ultrasonic action in order to keep the material being treated vibrating and thus to improve the washing action.
The method known from DE 19 14 095 thus likewise only describes the washing of the material to be treated and in particular does not describe the detoxification for which a decomposition of the mycotoxins is necessary.